It’s always challenging to determine what size pans to use for a cake. Search the web and you’ll find that cake serving guides vary significantly. Earlene’s Cake Serving Chart shows that a 9″ cake serves only 22 guests, while Aztec Rental shows that it serves 32. I’ve always relied on an old Wilton chart. My print copy shows considerable wear and tear in the form of stray pen marks, grease stains, and random notes. See?
For whatever reason, it’s really hard to find the Wilton chart online, so I’m sharing it here for easy reference. Keep in mind that the standard wedding cake slice is 1″ wide by 2″ deep by 4″ high, much smaller than a typical birthday or party cake slice. I tend to use the more generously-sized party cake chart (email me for a copy–I couldn’t find it online) if the cake is for a party rather than a wedding. Oh, I should mention that I use only 2″ deep pans and don’t recommend using 3″ deep pans because they take too long to bake resulting in a dry cake. Here’s the chart.